Knock-down load support



c. A. RHCH 2,230,015

KNOCK-DOWN LOAD SUPPORT Filed July 5, 1939 Patented Jan. 28, 194-1 onesrarss PATENT QFFlCE KNOCK-DOWN LOAD SUPPORT Application July 3, 1939,Serial No. 282,698

4 Claims.

This invention relates to load support devices, and more particularly tothose devices of the class comprising the so called collapsible stepladders.

An object of the present invention is to provide a collapsible stepladder or step stool of such construction as to be strong and rigid whenin an open or excnded condition for use.

A further object of the present invention is to provide a step stool asabove described which is adapted to be folded into a compact unit whichmay be easily handled and stored in a minimum of space.

Still a further object of the invention is to provide a collapsible stepstool having positive acting safety lock means associated therewithwhich will automatically set when the step stool is opened for use, andwhich requires a positive act on the part of an operator to release toefifect collapsing of said device.

Another object of the invention is to provide a collapsible step ladderhaving leg bracing means associated therewith to positively precludeaccidental collapse or relative movement of the ex- ,ended legs evenwhen said device is moved, slid or pushed along its supporting surface.

Still a further object of the invention is to provide a collapsible stepstool having means operatively associated therewith to lock said devicein a collapsed condition against accidental or unexpected opening.

Another object of the invention is to provide a collapsible stool ofsimple construction, which may be inexpensively manufactured and which.will give long trouble free service.

These and other objects are attained by the means described herein anddisclosed in the following drawing in which:

Fig. l is a perspective view of a step stool embodying the presentinvention in an extended position ready for use.

2 is side view of the device shown in 1 when in a folded, or collapsedposition.

Fig. 3 is an enlarged side view of the device showing a detailcomprising a part of the present invention.

Fig. l is a plan view of a linkage member comprising a detail of theinvention.

Fig. 5 is a side plan view of a modified form of a linkage membercomprising a detail ofthe invention.

Figs. 6 and '7 are side views of modified forms of ladder structuresembodying the present invention.

The primary object of the present invention is to provide a step stoolwhich when opened or extended for use will be rigid and positivelylocked against unexpected collapse.

Such a step stool may comprise two pair of spaced parallel uprights orstep support members 9 and II] which are pivotally connected at theirupper ends, as at it, to a suitable bracket or linkage member I l.

A top step or seat member 13 of any suitable material may be secured tobracket members H, by any suitable means such as rivets M, whereby theright and left sides of the unit are joined together. Since the rightand left sides of the unit are identical in construction just the rightside will be described hereinafter for brevity.

Parallel uprights 9 and H! are maintained in parallelism throughouttheir length by means of two or more spaced step-bracket or linkagemembers 39. Opposite ends of such linkage members are pivotallyconnected, as at M, to uprights ll and ill, as shown. Each step bracketor linkage member Ed is in parallelism with top linkage member I Iwhereby a parallel link structure is provided comprising uprights 9 andit and linkage members II and 3%.

Suitable steps l5 and iii are adapted to be disposed between opposed,parallel linkage members 3%], as shown.

A prop member ll, pivotally secured as at Hi to the overhanging portionof top linkage memher I i is provided, as shown.

A fixed linkage member 2b, is provided having its opposite endspivotally secured to upright member it as atxZl and to prop ll as at 22.This fixed linkage member will hereinafter be referred to as spacer bar28.

A second linkage member, hereinafter referred to as brace bar 23, ispivotally mounted at its lower end to upright it as at 26. Said bracebar is provided with a slot 25 which extends longitudinally thereof asclearly shown in Fig. 4. The end of slot 25 remote from pivotal point 24is provided with a lateral recess or ofiset 26, as shown.

A suitable pin 2'! secured to and extending from spacer bar 2!] isadapted for sliding and reciprocable engagement with slot 25 and offset25. If desired the head of said pin may be enlarged somewhat to preventsaid pin from becoming disengaged from said slot or offset.

As clearly shown in Fig. 2 pin 21 is disposed in the lower end of slot25 when the device is in a closed or collapsed condition, at which timeuprights 9 and Ill and prop ll assume the relative parallel positionsshown. Top step I3 and steps I5 and I6 are in parallelism with theirrear edges 32 disposed below their outer or forward edges 33, as shown.

The device may be extended or opened for use by lowering the forwardedge 33 of top step I 3 whereby linkage member II will be moveddownwardly about pivot I8. Movement of linkage II about pivot I8 causesspacer bar 20 to force upright member III laterally away from prop I I,and simultaneously therewith the free end of brace bar 23 is movedrelative to said spacer bar until pin 21 contacts the outer end I25 ofslot 25 whereupon it is deflected to seat within recess 26. When pin 27thusly engages recess 25 further relative motion of bracket II aboutpivot I8 is positively precluded and the upright members 9 and I II,prop I! and linkage members I I and 39 are locked in what is hereinafterreferred to as a fully extended position, as disclosed in Fig. 1.

Each step is prevented from turning about its longitudinal axis byreason of the fact that opposite ends thereof are secured to linkagemembers 39 of the parallel link structure, therefore since linkagemember II is locked in a horizontal plane, each step member is likewiselocked in a horizontal plane parallel to upper step I3.

It should be observed that the structure, when fully extended is strongand rigid, and that regardless of how a load or loads may be distributedupon top step I3 or upon steps I5 and I6 the structure will not toppleor collapse. It should be particularly noted that the application of aload L to the inner. edges of steps I5 and I6 and/or to the rear edge oftop step I3 will not and can not collapse said device, nor will theapplication of such load or loads result in relative movement betweenprop I'I, linkage I I and uprights 9 and II].

Furthermore it should be noted that the legs (prop I1 and uprights 9 andIII) of a fully extended structure (Fig. 1) are so locked againstrelative movement as to permit such a structure to be pushed or shovedbackwar-dly or forwardly over a supporting floor without the danger ofone or more of said legs striking an object or otherwise resistingmovement over the supporting surface so that other parts of thestructure could move relative to said leg or legs to tip or collapsesaid structure. of time when pin 21 of spacer member 29 is seated withinrecess 26 of brace bar 23, those portions of prop I1 and upright memberII] which are disposed between common link I I and spacer bar 29,comprise, along with said link and spacer bar, a trapezoid. Relativemotion or movement of any one of the sides (I1, 20, I9 and II) to theother sides is positively precluded so long as the relationship betweenpin 2? and recess 26 is maintained, as disclosed in Figs. 1, 3, 6 and 7.By reason of this fixed relationship these elements comprise the sidesof a fixed trapezoid.

In order to close or collapse such a device from its fully extendedposition it is necessary for the operator to intentionally lift or swingthe outer end of brace bar 23 about pivot 24 whereby to disengage pin 27from recess 26 and realign it with the longitudinal axis of slot 25.Upright members 9 and I9 may then be lifted relative to prop I! to closethe device into a compact unit as shown in Fig. 2.

If desired suitable resilient tips such as 56 During those periods maybe secured to the free lower ends of uprights 9 and II] and props IT, asshown.

In the preferred embodiment of the invention the lateral distance Abetween the lower ends of corresponding props I1 is greater than thelateral distance B between the lower ends of corresponding uprights 9and II], in order to give proper stability to the device when in a fullyextended position.

The lateral distance between props I'I' may be fixed by means ofsuitable tie rod members such as I9, which may be anchored together asat I99.

When the device is in a collapsed condition (Fig. 2) it often occursthat the weight of uprights 9 and II], steps I5 and I 6, linkage members39 and top step I3 will cause the device to suddenly and unexpectedlyswing open to an extended position. It has been found that bysubstituting a brace bar such as I23 (Fig. 5) for brace bar 23 thedevice may be positively locked in a collapsed or closed position. Bracebar I 23 is similar to 23 except for the provision of an offset recessI26 provided adjacent the lower end 225 of slot 25, as shown.

Pin 21 is adapted to automatically engage recess I 26 when the device isfully collapsed whereby the parts are locked against further relativemovement. Said device may be unlocked from its collapsed condition onlyafter the operator has lifted or swung the outer end of brace bar I23upwardly of pivot 24 whereby pin 21 is disengaged from recess I26 andaligned with the lower end of slot 25.

From the foregoing it is apparent that I have provided a step stooldevice having means asso ciated therewith for locking said device inboth an extended and collapsed position, and which locking means may bereleased only in response to an intentional act upon the part of anoperator.

In the preferred embodiment of the invention uprights 9 and I 9 andprops I 'I may be tubular members and the links 29 and 23 and braces I9may be of suitable flat metal stock. The tread portion of each step maybe suitably secured or anchored to the linkage members 39 which may beU-shaped in cross section, which in turn may be pivotally anchored touprights 9 and II] by suitable pivots 3I.

It should be observed that in some instances it may be desirable toprovide but one brace bar 23 and one spacer bar 29 in lieu of the twopair shown in Fig. 1.

It should be understood that instead of being pivotally connected tolinkage member II, as shown, the upper ends of props I1 and uprights 9and I0 may be pivotally secured to one or more individual bracketmembers I50, each of which may be independently anchored to top step IS,in which event the top step would comprise the common linkage memberfrom which the legs are secured, as disclosed in Fig. 6.

It should also be understood, that if desired, a single wide uprightstep carrying member IIII, Fig. '7, such as step frame 3 as disclosed inthe patents to Reed No. 1,644,856, and Cassidy No. 1,064,289, may besubstituted for the parallel uprights 9 and III. Such a member may bepivotally secured to linkage member II by any suitable means. Such anupright member would be capable of being locked in a fully extendedposition or in a collapsed position by means of spacer bars 29 and bracebars 23 in the same manner in which the spaced parallel uprights 9 andH) are locked relative to prop l1.

It should be understood that various modifications and changes in thestructural details of the device may be made, within the scope of theappended claims, without departing from the spirit of the invention.

What is claimed is:

1. In a device of the class described comprising a pair of spacedparallel uprights and a prop pivotally connected to a common linkagemember, a spacer bar, the opposite ends of which are pivoted to saidprop and to one of said upright members, a pin carried by said spacerbar, a brace bar one end of which is pivotally secured to theaforementioned upright member, the opposite end of said brace barincluding a slot extending longitudinally thereof and terminating at itsouter end in a recess offset from said longitudinal axis, said spacerbar pin adapted for reciprocable engagement with said brace bar slot andfor engagement with said offset recess to limit the degree of relativemovement between the free ends of said prop and said spaced paralleluprights, and linkage means for maintaining said upright members inconstant parallelism.

2. In a device of the class described comprising a pair of spacedparallel upstanding members interconnected by a plurality of parallellinks, one link including an overhanging portion, a prop memberpivotally secured to said overhanging portion, a spacer bar havingopposite ends pivotally secured to said prop and to one upstandingmember for permitting said upstanding members and prop to be collapsedto substantial parallelisms about a common link, a brace bar one end ofwhich is pivoted to the aforesaid upstanding member and including a slotextending longitudinally thereof terminating in an offset recessadjacent its outer end, a slot engageable member carried by said spacerbar adapted to engage said offset recess when the prop and upstandingmembers are fully extended from their collapsed position to lock saidparts in their relative extended positions.

3. In a device of the class described comprising a pair of spacedparallel upstanding members interconnected by a plurality of parallellinks, one link including an overhanging portion, a prop memberpivotally secured to said overhanging portion, a spacer bar havingopposite ends pivotally secured to said prop and to one upstandingmember for permitting said upstanding members and prop to be collapsedto substantial parallelisrns about a common link, a brace bar one end ofwhich is pivoted to the aforesaid upstanding member and including a slotextending longitudinally thereof, opposite ends of said slot terminatingin offset recesses, a slot and recess engageable member carried by saidspacer bar adapted to engage one offset recess to releasably lock thedevice in a fully extended position, and adapted to engage the otheroffset recess to releasably lock the device in a fully collapsedposition.

4. In a device of the class described, comprising a pair of spacedparallel uprights and a prop pivotally connected to a common linkagemember, a plurality of parallel steps the front and rear portions ofeach of which are pivotally connected to the parallel uprights wherebyto provide a parallel linkage structure, a spacer bar having oppositeends which are pivotally connected one each to said prop and to thatupstanding linkage member adjacent said prop and to which the rearportion of said steps are secured, a pin secured to and carried by saidspacer bar, a brace bar one end of which is pivotally secured to thesameupstanding member to which one end of said spacer bar is connected,said brace bar including an axial slot terminating at its outer end inan ofisetnotch, said slot adapted to slidably engage said pin when theprop and upstanding members are moved between collapsed and fullyextended positions, said notch adapted to releasably engage said pinwhen the prop and upstanding members are fully extended for locking themagainst unintentional relative movement, said brace bar and the rearportion of one step being secured to a common upright member by means ofa common pivot.

CHESTER. A. RICH.

